This invention relates to an improvement in keys, especially those which are used with axial pin tumbler locks. More particularly patent application, and to the manufacture thereof.
Many axial pin tumbler locks have a cylinder within which tumblers are slidable in a direction parallel to the axis of the cylinder. In a large proportion of such locks, the tumblers are arranged in a circular pattern, thus requiring a cylindrically shaped, so-called circular key to operate them. In the axial pin tumbler lock disclosed in the above referenced patent application, however, the tumblers are arranged in at least one planar row, so that they are operable by bittings located on a flat-bladed key.
Flat-bladed keys in general are known to the prior art. Some of them have longitudinally facing bittings adapted to cooperate with one or more rows of axially movable pin tumblers, as disclosed in U.S. Pat. Nos. 3,733,963 of Toepfer, 3,604,231 of Buschi, 2,036,747 of FitzGerald, 919,259 of Simpson, 219,815 of Keil, and 180,255 of Miller. 3,813,906 of Kerr and 450,745 of Lincoln are also somewhat relevant in this connection. But none of these keys is so designed as to take the fullest advantage of the flat blade configuration to provide maximum security, a great number of key changes, and minimal expense and difficulty of manufacturing commercially. Moreover, a number of the prior keys are readily duplicated, and the number of possible key changes provided by various key designs and lock and key combinations is relatively limited. Also, the bitting arrangement of certain of the keys is such that the bittings may engage or "pick up" tumblers other than those intended.
Prior art methods of manufacturing grooved keys have involved grinding grooves in key blades. In U.S. Pat. No. 3,729,965 of Gartner, it is recognized that manufacturing keys by grinding grooves in individual blades is expensive, and that a less costly approach is to extrude an elongated piece of blade stock with the desired grooves, thereafter cutting it to individual blade lengths. The key handles are manufactured separately, and attached to the individual blades afterwards.